Organic light emitting diodes (OLED) have several advantages, such as small size, long life span, low driving voltage, high responding speed, good shock resistance and low cost for large screen display production, which makes them suitable for applications that need to be light and thin. If the efficiency of the white light OLED can be further improved, it would be very applicable for a flat display, especially as a backlight source of a large screen LCD display that combines with color filters to produce various colors. Thus the development of a large screen white light OLED device is very important for the development of the full color flat display industry (especially for the LED display industry).